reStruct {nlme} | R Documentation

## Random Effects Structure

### Description

This function is a constructor for the `reStruct` class, representing a random effects structure and consisting of a list of `pdMat` objects, plus a `settings` attribute containing information for the optimization algorithm used to fit the associated mixed-effects model.

### Usage

    reStruct(object, pdClass, REML, data)
    ## S3 method for class 'reStruct':
    print(x, sigma, reEstimates, verbose, ...)

### Arguments

`object`

any of the following: (i) a one-sided formula of the form `~x1+...+xn | g1/.../gm`, with `x1+...+xn` specifying the model for the random effects and `g1/.../gm` the grouping structure (`m` may be equal to 1, in which case no `/` is required). The random effects formula will be repeated for all levels of grouping, in the case of multiple levels of grouping; (ii) a list of one-sided formulas of the form `~x1+...+xn | g`, with possibly different random effects models for each grouping level. The order of nesting will be assumed the same as the order of the elements in the list; (iii) a one-sided formula of the form `~x1+...+xn`, or a `pdMat` object with a formula (i.e. a non-`NULL` value for `formula(object)`), or a list of such formulas or `pdMat` objects. In this case, the grouping structure formula will be derived from the data used to to fit the mixed-effects model, which should inherit from class `groupedData`; (iv) a named list of formulas or `pdMat` objects as in (iii), with the grouping factors as names. The order of nesting will be assumed the same as the order of the order of the elements in the list; (v) an `reStruct` object.

`pdClass` | an optional character string with the name of the `pdMat` class to be used for the formulas in `object`. Defaults to `"pdSymm"` which corresponds to a general positive-definite matrix.
`REML` | an optional logical value. If `TRUE`, the associated mixed-effects model will be fitted using restricted maximum likelihood; else, if `FALSE`, maximum likelihood will be used. Defaults to `FALSE`.

`data`

an optional data frame in which to evaluate the variables used in the random effects formulas in `object`. It is used to obtain the levels for `factors`, which affect the dimensions and the row/column names of the underlying `pdMat` objects. If `NULL`, no attempt is made to obtain information on `factors` appearing in the formulas. Defaults to the parent frame from which the function was called.

`x` | an object inheriting from class `reStruct` to be printed.
`sigma` | an optional numeric value used as a multiplier for the square-root factors of the `pdMat` components (usually the estimated within-group standard deviation from a mixed-effects model). Defaults to 1.
`reEstimates` | an optional list with the random effects estimates for each level of grouping. Only used when `verbose = TRUE`.
`verbose` | an optional logical value determining if the random effects estimates should be printed. Defaults to `FALSE`.
`...` | Optional arguments can be given to other methods for this generic. None are used in this method.

### Value

an object inheriting from class `reStruct`, representing a random effects structure.

### Author(s)

Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates bates@stat.wisc.edu

### See Also

`pdMat`, `lme`, `groupedData`

### Examples

    data(Pixel)
    rs1 <- reStruct(list(Dog = ~day, Side = ~1), data = Pixel)
    rs1

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